Fix Ubuntu instalation doc.

Formatting, break `sudo ...` command into 2 lines.

Signed-off-by: Charles Chan <charleswhchan@users.noreply.github.com>

docs/installation/ubuntulinux.md

@@ -323,7 +323,8 @@ NetworkManager (this might slow your network).
 
 4. Restart both the NetworkManager and Docker.
 
-        $ sudo restart network-manager $ sudo restart docker
+        $ sudo restart network-manager 
+        $ sudo restart docker
 
 ### Configure Docker to start on boot